The present invention arose from a long standing problem that has existed in mitre joints and particularly the mitre joints of picture frames and the like. Picture frames may be glazed or unglazed, but in either case, a need exists for an inexpensive fastener which will permit the frames to be put together and taken apart easily. In the case of unglazed frames, the invention permits what would otherwise be a bulky structure, to be shipped and stored in knocked down form, thereby greatly reducing their cost to the ultimate consumer.
The picture frames with which we are more particularly concerned are fragile structures that may be quite thin in certain areas, and which may be made of relatively soft materials. In many instances, the prior art has abutted the members to be joined, and has driven fasteners into their ends to hold the mitre joint together. The prior art structures have included corrugated strips, and variously shaped wedges; and the driving of such fasteners into the ends of the members forming the mitre joint will split the members, if the wedges are not driven into the adjoining structures in a delicate manner.
An object of the present invention, therefore, is the provision of a construction of mitre joint having pockets in each of the ends of the members to be joined, and a foreshortenable fastener bridging the pockets in such manner that the fastener can be easily foreshortened to bring and hold the two ends of the members together.
Another object of the present invention is the provision of a new and improved joint of the above described type in which the pockets have a configuration that can be easily formed by a routing or milling operation that guides off of the joining surfaces.
Another object of the present invention is the provision of a new and improved foreshortenable fastener that is preferably made of a yieldable material that will accommodate and distribute the foreshortening forces over considerable areas of the members to be joined.
Still another object of the present invention is the provision of a new and improved fastener of the above described type which is made of a relatively soft material such as plastic so that it will not damage the end of the members being joined.
Further objects and advantages of the invention will become apparent to those skilled in the art to which the invention relates from the following description of the preferred embodiments described with reference to the accompanying drawings.